Can somebody, after attacking BTC, mine all the BTC in an hour or so?
No
Can everyone become helpless to just stop their mining operations completely whenever such a situation arise?
No
Will somebody be even interested in making money from this or the sole intention would just be the destruction of BTC as well as the network, and to gain Monopoly and establish the rules of centralization in crypto world?
It's a f* up world, so yeah, there might be people interested in it.
Yes this is correct. Looking at the total bitcoin currently in circulation as many as 18,339,725 BTC. If denominated in dollars, $ 130,393,610,777.50 at current prices. If counted 51% then there are around $ 66,500,741,496.3 or around 9,353,259.75 BTC. I think it is very difficult to bring down BTC, as long as special values and consensus are still trusted.
Hmm, you have something like 0.0051% of an idea what a 51% attack refers to, right?

It has nothing to do with price or currently mined coins, it's about the
hashrate of the network.
Since it's a US Act, good luck trying to use it, immediately after Missouri wins its case with China over the virus.
And who would be the culprit, an anonymous pool, the miners that provided the power?
The one that "hacked" or hacked the pool?
Even if caught, I have a feeling he will enjoy a lot of frappuccinos before getting two years in jail and then sightseeing around Tokyo, like the last guy that was in trouble over fraud.